1. Field of the Invention
The present invention relates to a camera module and a method of manufacturing the same, and more particularly to a camera module connected to an external substrate and including an image sensing module and an auto-focus (AF) module, and a method of manufacturing the same.
2. Description of the Related Art
A camera module that performs photographing operations is embedded in electronic devices, such as mobile phones, personal digital assistants (PDAs), notebook computers, and cameras (e.g., installed on back bumpers or doors). Such a camera module is very small to comply with the miniaturization requirements of mobile devices.
Typically, a camera module included in a miniature mobile device includes an image sensor module and a lens housing disposed on one side of the image sensor module. The image sensor module includes an image device, a circuit board electrically connected to the image device, a flexible printed circuit board (FPCB) for outputting the photographed images signals to an external circuit, and so on. At least one lens is installed in the lens housing, and an infrared (IR) filter may be further included in the lens housing.
The majority of image devices in digital cameras, for example, have an automatically focusing function performed by moving along an optical axis. Recently, the automatic focusing function has been embedded in camera modules too.
Referring to FIG. 1 which is an exploded perspective view of a conventional camera module 10, and FIG. 2 which is a side view of the camera module 10, the camera module 10 includes an image sensor module 20, an auto focus (AF) module 30, and a lens module 40.
The image sensor module 20 includes a first signal transmitting element 24 on which a conventional circuit pattern is formed, and an image sensing device 21 which photographs an image of an external object and is electrically connected to an external substrate.
A photographing area is formed on the image sensing device 21 which senses light energy incident from the outside and converts it into electrical signals. That is, the image sensing device 21 is a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).
The first signal transmitting element 24 may be a conventional printed circuit board (PCB). Alternatively, the first signal transmitting element 24 may be a flexible printed circuit board (FPCB) such as a tape carrier package (TCP) and a chip-on-film (COF), depending on where the image sensor module 20 is used.
In this case, one end of the first signal transmitting element 24 is coupled to the image sensing device 21, and a connector 27 is formed on the other end of the first signal transmitting element 24 so that the other end of the first signal transmitting element 24 can be coupled to the external substrate.
The AF module 30 may include at least one AF device (not shown) composed of a side sensor, a condenser lens (not shown) for focusing light onto the side sensor, and a location detecting element (not shown) for detecting a focusing location. The AF device, the condenser lens, and the location detecting element are accommodated inside an AF housing 31.
In addition, the AF module 30 includes a second signal transmitting element 34 coupled to the AF device, to transmit power and signals between the external substrate and the AF device.
The second signal transmitting element 34 may also be a conventional PCB, or a FPCB such as TCP and COF, depending on where the image sensor module 20 is used. In this case, one end of the second signal transmitting element 34 is coupled to the AF device, and a connector 37 is formed on the other end of the second signal transmitting element 34, to be coupled to the external substrate.
If the first and second signal transmitting elements 24 and 34 are FPCBs, they generally include a base layer formed of polyimide or polyester, and an insulating layer deposited on the circuit pattern.
The lens module 40 includes a lens housing 41 and at least one lens 42. The lens module 40 may further include a filter (not shown) to block infrared (IR) rays incident inside the lens housing 41 and to prevent refection of light incident inside the lens housing 41. The filter is installed at the bottom portion of a through-hole of the lens housing 41 from one side of the image sensing device 21. An IR-cut coating is disposed on the top portion of the filter, and an anti-reflection coating, which is for preventing reflection of light, is disposed on the bottom portion of the filter.
In this case, if the first signal transmitting element 24 provided in the image sensor module 20 and the second signal transmitting element 34 provided in the AF module 30 each include connectors 27 and 37 that are separately connected to the external substrate, the external substrate has to receive or supply signals and power separately from the connecter 27 of the image sensor module 20 and the connecter 37 of the AP module 30. Thus, the size of the camera module 10 is enlarged, and signal loss due to noise occurs.
However, in order to include the automatic focusing function in a conventional camera module, an additional AF module is required and such AF module needs to be connected to an external main board. Therefore, separate connecting ports are required since the image sensor module and the AF module need separate power ports and signal ports.
That is, assuming that a camera module is embedded in a mobile phone, a main board of the mobile phone has to supply signals and power to an AF module and an image sensor module. Thus, the overall structure of the camera module becomes complex.
Furthermore, since the camera module and the AF module have separate power ports, signal loss due to noise occurs.